Instant Scripts are free scripts (with pro-versions available, moderately priced) for architectural modeling inside SketchUp, created by Vali Architects. Nice story too: after a long time working in AutoCAD and writing scripts in AutoLisp he currently has more fun in SketchUp, yet still tries to be productive.
- Instant Roof
- Instant Road
- Instant Site Grader
Example of what you could create with the Instant Roof script: